Effects of rotational speed and fill level on particle mixing in a stirred tank with different impellers

doi:10.1016/j.cjche.2017.11.010

摘要/Abstract

摘要： The particle mixing was studied in a cylindrical stirred tank with elliptical dished bottom by experiments and simulations. The impeller types used were double helical ribbon (HR) + bottom HR, pitched blade ribbon + bottom HR, inner and outer HR + bottom HR, and pitched blade ribbon + Pfaudler + bottom HR labeled as impellers I to IV, respectively. The quantitative correlations among the rotational speed, fill level and power consumption for impeller I and impeller Ⅱ were obtained by experiments to validate the discrete element method (DEM) simulations. The particle mixing at different operating conditions was simulated via DEM simulations to calculate the mixing index using the Lacey method, which is a statistical method to provide a mathematical understanding of the mixing state in a binary mixture. The simulation results reveal that as the rotational speed increases, the final mixing index increases, and as the fill level increases, the final mixing index decreases. At the same operating conditions, impeller Ⅲ is the optimal combination, which provides the highest mixing index at the same revolutions.

关键词: Particle, Mixing, Discrete element method (DEM), Rotational speed, Fill level, Lacey index

Abstract: The particle mixing was studied in a cylindrical stirred tank with elliptical dished bottom by experiments and simulations. The impeller types used were double helical ribbon (HR) + bottom HR, pitched blade ribbon + bottom HR, inner and outer HR + bottom HR, and pitched blade ribbon + Pfaudler + bottom HR labeled as impellers I to IV, respectively. The quantitative correlations among the rotational speed, fill level and power consumption for impeller I and impeller Ⅱ were obtained by experiments to validate the discrete element method (DEM) simulations. The particle mixing at different operating conditions was simulated via DEM simulations to calculate the mixing index using the Lacey method, which is a statistical method to provide a mathematical understanding of the mixing state in a binary mixture. The simulation results reveal that as the rotational speed increases, the final mixing index increases, and as the fill level increases, the final mixing index decreases. At the same operating conditions, impeller Ⅲ is the optimal combination, which provides the highest mixing index at the same revolutions.

Key words: Particle, Mixing, Discrete element method (DEM), Rotational speed, Fill level, Lacey index

Yuyun Bao, Yu Lu, Ziqi Cai, Zhengming Gao. Effects of rotational speed and fill level on particle mixing in a stirred tank with different impellers[J]. Chinese Journal of Chemical Engineering, 2018, 26(6): 1383-1391.

Yuyun Bao, Yu Lu, Ziqi Cai, Zhengming Gao. Effects of rotational speed and fill level on particle mixing in a stirred tank with different impellers[J]. Chin.J.Chem.Eng., 2018, 26(6): 1383-1391.

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